This invention relates generally to apparatuses for recording and reproducing information signals on and from a recording medium. More particularly the invention relates to a floating type magnetic head assembly suitable for use in high-density magnetic recording and reproducing signals on and from a moving recording medium.
In apparatuses for recording and reproducing (hereinafter referred to as R/R) using magnetic discs as magnetic recording mediums, a prime requirement is that the R/R of signals be accomplished stably without damaging the surfaces of the magnetic recording mediums. For fulfilling this requirement, it has been a general practice in the prior art to provide and adapt means for operating the magnetic head in a state wherein its magnetic gap part is floating relative to the surface of the magnetic recording medium with a specific minute spacing therebetween. The magnetic head is thus operated at the time of recording an information signal on the magnetic disc and also at the time of reproducing an information signal from the magnetic disc.
Among the possible problems encountered in R/R operation which must be overcome is excessive variation of the flotation clearance of the magnetic head due to fluctuation or wavy motion of the magnetic disc surface when it is rotating. Another requirement is the assurance of smooth contact-start-stop operation and load-and-unload operation. In order to satisfy these and other requirements, floating magnetic head devices of parent-child type as disclosed in, for example, Japanese Patent Publn. No. 18667/1969 have been proposed.
In this parent-child type of floating type magnetic head device, two sliders, namely, a parent slider and a child slider supporting a magnetic head are provided. During operation these two sliders are respectively in a state of buoyancy or flotation above the surface of the magnetic recording medium due to an aerodynamic lift force acting on the flotation surfaces of the slider parts. This lift force is produced by a thin-layer gas (air) flow between the surface of the magnetic recording medium and the flotation surface of the slider parts. By this provision, variations in the flotation clearance of the sliders is reduced, whereby stable flotation of the sliders is maintained. Furthermore, vibration or resonant oscillation induced by external disturbance in the slider supporting mechanism is suppressed whereby stable flotation operation can be accomplished.
In a floating type magnetic head device of known parent-child type, however, it has been customary to form stably a relatively large flotation gap above the magnetic recording medium surface of the magnetic disc for purposes such as achieving stable operation and eliminating mechanical resonance. For this reason, such a magnetic head device has not been suitable for realizing high-density recording. In recent years, however, there has been an increasing necessity for magnetic R/R apparatus of miniature size yet large capacity. Accordingly there is a demand for the development of technology capable of accomplishing highdensity R/R operation with a magnetic head floating in a position much closer than hitherto above the magnetic recording medium surface of a magnetic disc.
In the case where high-density R/R operation is carried out in the above described manner, dust particles adhere to and collect on the magnetic gap surface functioning as the flotation surface. As the quantity of this dust gradually increases, the dust particles infiltrate into and fill the gap between the flotation surface of the floating type magnetic head and the magnetic recording medium surface of the magnetic disc. As a consequence, the recording medium surface of the disc becomes abraded and becomes overheated or otherwise damaged. Accordingly there is a need for a solution to this problem.
In order to accomplish high-density R/R by means of a floating type magnetic head, it is necessary to cause a slider device to float so that the magnetic gap surface of the magnetic head floating above the magnetic recording medium surface and this medium surface are in a mutually very close state. A magnetic recording medium having a large coercive force is suitable for high density magnetic R/R. Even with such a medium, in the case where this slider device in this state is thus buoyed up, an amply satisfactory recording operation can be carried out with respect to this magnetic recording medium with a magnetic head in which an ordinary bulk ferrite core is used, and which is in a state wherein a recording current of an order that will not give rise to magnetic saturation is passed therethrough. Furthermore, the gap loss at the time of reproduction is small. Therefore it becomes possible to realize high-density R/R by means of a floating type magnetic head.
In a floating type magnetic head of the prior art, however, its slider is large in size and also has a large mass. Furthermore, the slider has not been of a character to have ample response relative to the magnetic recording medium surface. Therefore, R/R operation is carried out with the slider in a floating state and in position which is extremely close to the recording medium surface. In this case, there is a possibility of contact or even collision between the slider and the recording medium. In such an event, instantaneous damage or breakage of the magnetic head and the recording medium is apt to occur.
Another undesirable possibility is the infiltration of dust into small crevices or recesses in the slider floating thus in extreme close proximity to the medium surface. In the case where dust particles adhere to other parts, the dust accumulation tends to grow under a snow-balling effect. The dust then gives rise to abrasive rubbing of the recording medium and contacting. As a consequence, the magnetic head and the recording medium are damaged or broken. Thus it has not been possible to carry out R/R operation with a known floating type magnetic head caused to float in a positional state of extremely close proximity to the recording medium. Therefore it has been difficult to realize high density recording by use of any floating type magnetic head known in the prior art.